In this study, a batch of indium tin oxide (ITO)/Sn composites with different ratios was obtained based on the principle of thermal evaporation by an electron beam. The crystalline structure, surface shape, and optical characterization of the films were researched using an X-ray diffractometer, an atomic force microscope, a UV-Vis-NIR dual-beam spectrophotometer, and an open-hole Z-scan system. By varying the relative thickness ratio of the ITO/Sn bilayer film, tunable nonlinear optical properties were achieved. The nonlinear saturation absorption coefficient β maximum of the ITO/Sn composites is -10.5×10-7cm/W, approximately 21 and 1.72 times more enhanced compared to monolayer ITO and Sn, respectively. Moreover, the improvement of the sample nonlinear performance was verified using finite-difference in temporal domain simulations.

Various coatings in high-power laser facilities suffer from laser damage due to nodule defects. We propose a nodule dome removal (NDR) strategy to eliminate unwanted localized electric-field (E-field) enhancement caused by nodule defects, thereby improving the laser-induced damage threshold (LIDT) of laser coatings. It is theoretically demonstrated that the proposed NDR strategy can reduce the localized E-field enhancement of nodules in mirror coatings, polarizer coatings and beam splitter coatings. An ultraviolet (UV) mirror coating is experimentally demonstrated using the NDR strategy. The LIDT is improved to about 1.9 and 2.2 times for the UV mirror coating without artificial nodules and the UV mirror coating with artificial nodule seeds with a diameter of 1000 nm, respectively. The NDR strategy, applicable to coatings prepared by different deposition methods, improves the LIDT of laser coating without affecting other properties, such as the spectrum, stress and surface roughness, indicating its broad applicability in high-LIDT laser coatings.

研究设计和制备了中心波长为1 064 nm的45°多层膜反射镜，通过数值仿真结合实验，对薄膜中节瘤缺陷引起的电场增强效应及其对薄膜抗激光损伤性能的影响进行了研究。结果表明：当1 064 nm激光从右至左45°斜入射时，电场增强效应主要出现在节瘤缺陷的表层及其左侧轮廓中部，电场增强效应随节瘤缺陷尺寸增大而增强。实验上，在清洁的基板表面喷布单分散SiO₂微球作为人工节瘤种子，采用电子束蒸发制备法完成多层全反膜的制备，采用R-on-1方式对薄膜样品进行激光损伤测试。结果表明，薄膜的损伤阈值随着节瘤缺陷尺寸增加而减小。通过综合分析电场增强效应、薄膜损伤测试结果及损伤形貌特征得出，薄膜损伤阈值降低是由于节瘤缺陷和薄膜中微缺陷共同作用的结果。